wireless N, also how old is the pc? if its older then 6yrs pci maybe your only option if its withen past 6-8yrs then you might have the option of either however if its withen the past say 5years then youd prolly want a wireless-N pci-e as far as installing it install it to the only slot it will fit in. and if you want to air on the safe side I believe most pc's have a pci slot so wireless-n card pci

there is a difference between a pci and a pci-e any one inch slots will be your pci-e 1 and 4x. your longer slots excluding ones like where the graphics card is installed in will be your pci slots generally these are brown color I believe